Power presses are built in a wide variety of styles and sizes, and those presses have a variety of applications. In many applications, a press is used to operate at a high rate. The press moves quickly in its pressing stroke and moves at substantially the same rate in its return stroke. As is well known, die cushions are used as a work holding device or part ejector. The cushion which is used in certain instances includes a resilient bellows or actuator. The actuator receives a compressible fluid such as air so that the lower portion of the die may travel a selected distance with the ram during the pressing operation.
Once the actuator of the cushion is compressed, and the ram starts its return stroke, the cushion moves the movable portion of the die with it, disengaging the workpiece. The die cushion actuator moves the lower portion of the die with a constant acceleration until the movable portion of the lower die is at its rest position. The lower portion of the die is provided with a stop which causes an abrupt halt to the movement of the die. This abrupt halt causes an impact loading on that portion of the die connected to the cushion and associated parts. The repeated impact loading on the parts of the die often causes damage to those parts.
It is desirable to provide a die cushion construction for use in a press wherein the stopping of the die is not an abrupt stop but rather a substantially smooth stop which reduces damage to the die by impact loading on the die. This construction also reduces damage to the press and the die cushion itself.